1. Field of the Invention
The present invention relates to image pickup apparatuses such as electronic still cameras and digital video cameras, and more particularly, to an image pickup apparatus for taking an image including only a background image but not an object and an image including the object.
2. Description of the Background Art
Japanese Patent Laying-Open No. 10-21408 discloses, for example as a conventional image pickup apparatus of this type, a technique of automatically extracting an object region from a moving image with stable accuracy and at a high speed independently of the shape of the object and the characteristic of image data by using a background image and an object image.
In the conventional example, the object image and the background image are taken in the same mode so as to minimize a difference between image data corresponding to the background. After the images are taken, differential data of the background and object images is produced. Further, the differential data is averaged and subjected to a process utilizing a threshold value. Thereafter, the region of the object is extracted based on the difference between the image data of the background and object images. The extracted image data are compressed, encoded, and recorded.
However, in general cases including the above mentioned example, a shutter must be pressed twice to input (take) background and object images. If an image pickup apparatus is fixed by a tripod or the like, the pickup apparatus slightly moves when pressing the shutter. This results in a problem that the background image and a portion of the object image corresponding to the background do not completely match.
To avoid this problem, a background without any pattern, such as a plain colored wall, has often been used. In this case, an adverse effect due to the slight movement of the image pickup apparatus can be avoided. However, it is extremely difficult to prepare a plain colored background for normal, and especially outdoor picture taking.
The image pickup apparatus may be designed such that the shutter can be pressed by a remote controller. However, this increases the cost of the image pickup apparatus and results in another problem that the remote controller must be carried on.
Another possible approach is that the shutter is pressed by a release as in a normal optical camera. However, even if the shutter button would not be directly pressed, the image pickup apparatus may still be moved slightly due to connection to the release, thereby causing another problem that a person other than the object is required for picture taking.